Holography is a recording and reproducing technology to record and reproduce a real three-dimensional image of an object by using the principles of interference and diffraction of light. A first step of the holography is to record (or photograph) light wave information of an object by using the principle of interference. An object to be photographed generates a diffuse reflection object beam upon being irradiated by a split beam of a laser beam, and another split beam of the laser beam irradiates a holographic film as a reference beam to meet and interfere with the object beam, so that a phase and an amplitude of each point on the object beam (i.e., a light wave of the object) are transformed into a spatially varying intensity, and the light wave of the object is completely recorded by using a contrast and an interval between interference fringes. A second step of the holography is to reproduce the light wave information of the object by using the principle of diffraction.
During the process of reproduction (i.e., image formation), upon being irradiated by a coherent laser beam (e.g., the same laser beam as the reference beam), a diffraction light wave of a linearly recorded sine-type hologram may generally provide two images, which are an original image (also known as an initial image) and a conjugate image. A reproduced image has a true three-dimensional sense and a real visual effect.
A digital hologram display device realizes holographic stereoscopic display by means of a photoelectric modulation device. However, an existing digital hologram display device can display only one hologram screen and the viewable region thereof is small, which is not suitable for viewing by a plurality of viewers at the same time.